Sheet shuttle feed

ABSTRACT

A vacuum-type sheet feeding device is described which comprises a reciprocating shuttle plate having a gated vacuum groove. In operation, as suction is applied to the groove and a sheet to be fed is thereby sucked into the groove, the vacuum gate, which closes off one end of the vacuum groove, yields to allow the sheet to move into the groove. The sheet feeding apparatus also includes a sheet magazine which comprises a separating ledge for supporting a bottom front corner of a sheet stack, a sucker cup for pulling the bottom sheet (the sheet to be fed) off of the separating ledge, and adjustable lifters for supporting the rear corners of the stack at different heights. In addition, the sheet feeding apparatus includes a throat-knife mechanism which comprises a narrow throat knife mounted on a pivoted throat-knife bracket. If the pivoted throat-knife bracket is in an active position, the throat knife protrudes downwardly in front of the shuttle-plate grove when the shuttle plate is under a sheet stack, and adjacent to the shuttle-plate groove when the shuttle plate is feeding.

llnited States Patent 11 1 Morrison 1451 Oct. 29, 1974 [73] Assignee: Bell and Howell Company,

Phillipsburg, NJ.

22 F11C1Z Sept. 27, 1973 21 Appl. No.2 401,413

Related US. Application Data [63] Continuation-impart of Ser. No. 296,556, Oct. 11,

1972, abandoned,

435,327 10/1967 Switzerland 271/99 Primary ExaminerEvon C. Blunk Assistant Examiner-Bruce H. Stoner, Jr. Attorney, Agent, or FirmGriffin, Branigan and Butler 5 7 ABSTRACT A vacuum-type sheet feeding device is described which comprises a reciprocating shuttle plate having a gated vacuum groove. In operation, as suction is applied to the groove and a sheet to be fed is thereby sucked into the groove, the vacuum gate, which closes off one end of the vacuum groove, yields to allow the sheet to move into the groove. The sheet feeding apparatus also includes a sheet magazine which comprises a separating ledge for supporting a bottom front corner of a sheet stack, a sucker cup for pulling the bottom sheet (the sheet to be fed) off of the separating ledge, and adjustable lifters for supporting the rear corners of the stack at different heights. in addition, the sheet feeding apparatus includes a throat-knife mechanism which comprises a narrow throat knife mounted on a pivoted throat-knife bracket. if the pivoted throat-knife bracket is in an active position, the throat knife protrudes downwardly in front of the shuttle-plate grove when the shuttle plate is under a sheet stack, and adjacent to the shuttle-plate groove when the shuttle plate is feeding.

15 Claims, 6 Drawing Figures 38441551 SHEET 1 or 2 PAIENIEB 29 FIG. 3

llli II SHEET SHUTTLE FEED This is a continuation-in-part application of U.S. Pat. application Ser. No. 296,556, filed Oct. II, 1972 now abandoned, and entitled Sheet Shuttle Feed.

BACKGROUND OF THE INVENTION This invention relates broadly to the art of sheet feeding devices and more particularly to vacuum-type sheet feeding devices.

Some vacuum-type sheet feeding devices comprise reciprocating shuttle plates positioned at the bottoms of sheet stacks. The cycle of operation for these shuttle plates is normally as follows: A suction is applied through the shuttle plate to the bottom sheet in the sheet stack, thereby adhering the bottom sheet to the shuttle plate. The shuttle plate then moves forwardly carrying the bottom sheetwith it and delivers this sheet to rollers or other gripping means. At this point, the suction is turned off and the shuttle plate returns to its position under the sheet stack.

In some such systems, knives or other blocking structures are used to restrain other sheets in the sheet stack from moving with the shuttle plate; and in some such systems the sheet stack rests on one or more ledges from which the bottom sheet is pulledprior to being fed forwardly by the shuttle plate.

One difficulty with some prior-art vacuum-type sheet feeding devices is that suctions, or partial vacuums, applied by shuttle plates, bleed through bottom sheets and cause second-from-bottom sheets to adhere to the bottom sheets. When this happens, two sheets are fed forwardly by the shuttle plates. Thus, it is an object of this invention to provide a shuttle plate for a vacuumtype sheet feeding device which substantially avoids this bleed-through problem and thereby reduces the number of double feeds.

It is possible to reduce double feeds by reducing the amount of suction applied to the bottom sheets; however, such a method also reduces the strength with which the shuttle plate holdsthe bottom sheet while moving it forwardly. Therefore, it is also an object of this invention to provide a vacuum-type sheet feeding device which'reduces the possibility of a double feed but yet does not reduce the strength with which the shuttle plate holds the bottom sheet while feeding it.

In systems which employ blocking structures in front of shuttle plates to prevent other sheets from following the bottom sheet there is a difficulty in that the position of the blocking structure is somewhat critical. That is, if it is too high, it may allow the-second from bottom sheet to follow the bottom sheetand if it is too low it may prevent a thick bottom sheet from being fed. This problem is magnified when very thin sheets are being fed. Thus, it is an object of this invention to provide a shutte-plate-sheet feeding device which employs a throat knife theposition of which is not unduly critical.

With regard to feeding envelopes, it is sometimes difficult to separate'a bottom'envelope, forsome" types of envelopes, by means of a ledge and a pneumatic puller because the envelopes adjacent to-the bottom envelope tend to follow'it off the ledge. This causes double feeds. On the other hand, it is also sometimes difficult to separate some other types of envelopes with a throat knife because loose envelope edges and windows tend to catch on the knife. Thus, it is an object of this invention to provide a vacuum-type sheet feeding device which combines both types of sheet separating mechanisms so as to retain their respective advantages while reducing their disadvantages.

Yet another problem with some prior-art vacuumtype sheet feeding devices is that they do not always function properly when sheet stacks are warped. The reason for this is that if the sheet stacks have warped shapes the bottom sheets may not make good contact with the tops of the shuttle platesThus, it is yet another object of this invention to provide a vacuum-type sheet feeding device which can compensate for warped sheet stacks.

SUMMARY OF THE INVENTION According to principles of this'invention, a vacuum groove in the top of a shuttle plate isclosed at one end by means of a vacuum-groove gate. However, the vacuum-groove gate allows sheets to be pulled down into the groove when suction is applied within the groove.

At this point the shuttle plate feeds the bottom sheet.

forwardly. v

Further, the sheet feeding apparatus includes a throat-knife mechanism which comprises a narrow throat knife mounted on a pivotal throat-knife bracket. If the pivotal throat-knife bracket is in an active position, the throat knife protrudes downwardly in front of the shuttle plate when it is under a sheet stack, and adjacent the shuttle-plate groove when the shuttle plate is feeding. The throat knife can be pivoted to an inactive position.

The magazine further includes two adjustable lifters, each being located at respective rear corners of the sheet stack. When the sheet stackis warped, one or both of the lifters can be raised or lowered to thereby compensate for the warpage and cause the bottom sheet of the sheet stack to make good contact with the top of the shuttle plate. The-adjustable lifters have handles extending upwardly with which'they can easily be gripped by an operator and thereby raised or lowered. The adjustable lifters are clamped in position by handtightened knobs once they are set in proper positions.

- BRIEF DESCRIPTION OF THE DRAWINGS ings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention in a clear manner.-

FIG. 1 is an isometric view of a vacuum-type sheet feeding device employing principles of this invention;

FIG. 2 is a front view of the device depicted in FIG. 1;

FIG. 3 is a side view of the device depicted in FIG. 1'.

FIG. 4 is a secional view of the shuttle plate employed in the device of FIG. 1 taken on line 4-4 of FIG. I; and

FIG. 5 is a front view of portions of the device of FIG. 1;

FIG. 6 is a simplified isometric view of the shuttle plate of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, a vacuum-type sheet feeding device comprises a sheet-stack magazine 10 which includes front guides 11 and 12, a separating ledge 14, side guides 15, a rear guide 17 and adjustable lifters 16 and 18. The arrangement of the side and rear guides 15 and 17 is somewhat simplified herein for the purposes of clarity because they are not a significant part of this invention. Also, an overall frame which interconnects the guides as well as other elements of the device described herein are not depicted in the drawings in order to more clearly depict the important features of the invention.

A suction-separating apparatus includes a shuttle plate 19, having a suction groove therein, and a sucker cup 22.

As can be seen in FIGS. 1, 2 and 3, the magazine holds a sheet stack 24. In this regard, the left-hand forward corner of the sheet stack 24 is supported by the separating ledge 14, the rear right and left-hand corners of the sheet stack 24 are supported by hooks of the adjustable lifters 16 and I8, and the forward center portion of the sheet stack 24 is supported by the top surface of the shuttle plate 19.

The front guides I1 and 12 are positioned in front of the sheet stack 24, the side guides 15 are positioned at the sides of the sheet stack 24, and the rear guide 17 is positioned at the rear of the sheet stack 24 between the adjustable lifters l6 and 18 and the rear of the sheet stack. Thus, the sheet stack is guided on all sides.

It should be noted that the top surface of the shuttle plate 19 is positioned below the bottom end of the forward guide 12 by a distance a.

The top surface of separating ledge 14 is even with the top surface of shuttle plate 19.

With reference to FIGS. 4 and 5, the suction groove 20 of the shuttle plate 19 is tapered upwardly to the top surface of the shuttle plate 19 at the right-hand end thereof (FIG. 4) and extends to the edge of the shuttle plate at the left-hand end thereof. The suction groove 20 has a perforate false bottom 26 which encloses a suction distributing space 28. The suction distributing space 28 communicates with a suction source (not shown) via a suction groove line 30 and a suction groove valve 32.

The left-hand end of the suction groove (FIG. 4), which extends to the edge of the suction plate 19, is covered by a suction groove gate 34 which comprises two pivotable half-gates 36. The pivotable half-gates 36 are pivotally attached to the forward end of the shuttle plate by pins 38 (FIG. 5). The pivotable half-gates 36 are biased upwardly by cantilevered piano-wire springs 40 (FIGS. 4 and 5) which also serve as stops to limit the upward travel of the half gates. Tapers 41 on the tops of the half-gates 36 permit sufficient clearance to allow the two halfgates 36 to swing freely downward around the pins 38.

The shuttle plate 19 has forwardly and rearwardly reciprocating movement as shown by an arrow 42 (FIGS. 1 and 3). The sucker cup 22 has up and down reciprocating movement as indicated by an arrow 44 in FIGS. 1 and 3.

The sucker cup 22 is connected via a sucker cup valve 46 (FIG. 2) to a suction source (not shown).

It can be seen in FIGS. 1 and 3 that the adjustable lifters 16 and 18 are vertically adjustable with respect to each other and frame members so that the rear left and right-hand corners of the sheet stack 24 can be set at different height levels. In this regard, the adjustable lifters l6 and 18 are vertically movable in vertical bores in frame members 45 and may be clamped in position on the frame members 45 with hand-tightened knobs 47 (FIG. 3) having a threaded shaft 48, once the lifters have been positioned. The threaded shafts 48 screw into the frame members 45 and extend through to the frame-member bores. It should also be noted that the adjustable lifters 16 and 18 have handles which extend upwardly thereby enabling an operator to easily lift or lower the adjustors. In addition, the lifters can also be positioned laterally so that they can be placed in an appropriate lateral position for various widths. In this regard, the frame members 45 are mounted for individual lateral movement on a slotted beam 51, for example.

FIG. 6 depicts the upper surface of the shuttle plate 19 on which are formed saw-toothed frictional elements 49. These elements are exaggerated in FIG. 6 for purpose of illustration. The frictional elements 49 enhance the grip with which the shuttle plate 19 grips sheets.

A throat-knife mechanism 50 includes a protruding throat knife 52, a throat-knife bracket 54, a throatknife-bracket pivot member 56, and a clamping screw 58. It should be noted that the throat-knife bracket 54 has a slot 60 therein which registers with the clamping screw 58. The clamping screw 58 screws into the front guide 11 so that its head 62 can be made to clamp the throat-knife bracket 54 to the front guide 11. The throat knife 52 is attached to the throat-knife bracket and can, therefore, be rotated to an active position as depicted in solid lines in FIGS. 1, 2 and 5 or to an inactive position as depicted in dashed lines in FIG. 1. The tapers 41 on the tops of the half-gates 36 form an indentation at the tops of the half-gates 36 which allows the throat knife 52 to be set below the top surface of the shuttle plate 19 (the paper rest level). Otherwise, the throat knife 52 could not very well be placed below the half gates 36 because it would hit them on a return stroke of the shuttle plate 19. In the preferred embodiment, the throat knife 52 is no wider than the suction groove 20.

In operation, when a bottom sheet 64 of the sheet stack 24 is to be separated from the stack, the sucker cup 22 moves upwardly and the sucker-cup valve 46 opens; thus, the sucker cup 22 grips the left-hand front corner of the bottom sheet 64 of the stack 24. At this point, the sucker cup 22 movesdownwardly carrying this corner of the bottom sheet 50 with it. Thus, the bottom sheet 64 is pulled off the ledge 14. Next, the sucker cup valve 46 closes so that the sucker cup 22 releases the bottom sheet 64. This procedure provides a first separation between the bottom sheet 64 and the next-to-the-bottom sheet 66.

Simultaneously therewith, the suction groove valve 32 opens thereby causing suction in the suction distributing space 28 of the suction groove 20. This suction is distributed throughout the suction groove as shown in FlG. 5. As the bottom sheet 64 enters the suction groove 20 the pivotal half gates 36 yield downwardly. The suction groove 20 is deep relative to its width. lt-is difficult for the next-to-bottom sheet 66 to follow the bottom sheet 64 into the suction groove 20 under the influence of bleed-through vacuum because the narrowness of the groove makes the beam strength of the paper across this gap higher than if the groover were wider. Therefore, the bottom sheet 64 is tightly gripped by the shuttle plate 19, but the next-to-bottom sheet 66 is not. Thus, a second separation between these two sheets is accomplished.

At this point, the shuttle plate 19 moves forwardly carrying the bottom sheet 64 with it. The frictional elements 49 aid the shuttle plate 19 in gripping the bottom sheet 64 as it moves forwardly. As the shuttle plate moves forwardly carrying the bottom sheet 64 which is pulled down into the suction groove 20, the throat knife 52, when it is in the active (solid line) position, blocks the movement of sheets trying to follow the bottom sheet 64. Thus, still a third method of separation is provided. Eventually, the bottom sheet 64 is transferred to a gripping mechanism and the suction groove valve 32 closes thereby causing the shuttle plate to release its grip on the bottom sheet 50. The shuttle plate then returns to its position under the sheet stack 24 and the cycle is repeated.

Should warpage of the sheet stack 24 be such that it is difficult for the shuttle plate 19 to grip the bottom sheet, the shape of the sheet stack can be adequately adjusted by lifting or lowering one or both of the adjust-- able lifters l6 and 18,

it should be appreciated by those skilled in the'art that the yieldable suction-groove gate 34, including the pivotable half gates 36, seal off the end of the suction groove 20, so that adequate suction reaches the bottom sheet 64, but yet allows the bottom sheet to-be pulled down into the groove. At the same time, the deep, narrow suction groove 20, although applying great suction force to a bottom sheet, makes it difficult for a next-tobottom sheet to follow the bottom sheet into the groove. in this regard, when the bottom sheet is pulled into the groove, a space or passage opens-up betweenthe bottom sheet and the next-to-bottom sheet which allows atmospheric air to rush in and neutralize any vacuum bleed between these two sheets.

in addition, the vacuum groove is deep so that depression of a sheet into this groove by'suction forms a detent between the sheet and the groove which provides better than average traction for moving the sheet from beneath a sheet stack.

It should also be appreciated that this device provides next-to-bottom sheet so that the chance of having dou-.

ble feeds is reduced. In this regard, with some types of envelopes, envelopes tend to follow the bottom-envelope off the separating ledge 14; however, the suction groove 20 and the throat knife 52 provide backup mechanisms by separating such following envelopes from the bottom envelope when it is fed by the shuttle plate 19.

knife 52 the throat knife can be moved to an inactive I position as shown in dashed lines in FIG. 1. In this respect, however, with reference to FIG. 5, when the bottom sheet 64 is pulled down into the groove 20, a relatively large space separates the throat knife 52 from the bottom sheet 64. Because of this, windows and loose seams do not catch on the throat knife 52 as often as is the case for most blocking-structure-type sheet separators. This feature also makes the vertical position of the throat knife less critical since a separating slot must not be one sheet width wide. Also, this feature alldws the throat knife 52 to be set below the paper-rest level so that it more effectively blocks sheets not sucked into the groove. Further, in this connection, because the throat knife 52 is no wider than the suction groove 20 (and is preferrably somewhat narrower) it does not contact arched portions of the bottom envelope 64 which flare up on each side of the groove. Further, the narrow throat knife does not block the bottom envelope in areas where it is not controllably pulled down into the suction groove.

It can be appreciated by those skilled in the art, that the vacuum-type sheet feeding device disclosed herein is more efficient than many prior-art sheet feeding devices.

While this invention has been particularly shown and described with reference to a preferred embodiment, it will be understood-by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the in vention. For example, various arrangements of valves could be used with this invention. In addition, various magazine structures could also be employed.

The embodiments of the invention in which an exclusive property or privilege are claimed are defined as follows: v

l. -A vacuum-type sheet feeding device for feeding the bottom sheet from a stack of flat sheets, said device comprising:

a movable shuttle plate having a surface on which said stack rests, for gripping said bottom sheet and pulling said bottom sheet out of said sheet stack,

said movable shuttle plate having motion in a direction substantially parallel to the plane of said flat sheets, said surface defining an elongated narrow groove therein which is elongated in a direction parallel to said direction of said shuttle-plate motion, and said narrow groove terminating at a back end thereof so that said back end is closed off and said groove extending to an edge of said shuttle plate at a front end thereof so that said front end is open;

gate mounted on said shuttle plate for closing off said groove near said front end, but for yielding to allow said bottom sheet to be sucked into said 3. A vacuum-type sheet feeding device as claimed in claim 1 wherein is further included;

a magazine for holding said sheet stack said magazine including a ledge for supporting one corner of said sheet stack; and

a separating means for disengaging the corner of the bottom sheet of said sheet stack from said ledge.

4. A vacuum-type sheet feeding device as claimed in claim 3 wherein said separating means comprises a reciprocating sucker cup which pneumatically grips the bottom sheet of said sheet stack and pulls said sheet off said ledge.

5. A vacuum-type sheet feeding device as claimed in claim 1 wherein is further included:

a magazine for holding said sheet stack; and

adjustable lifters for providing supports for each of the rear corners of said sheet stack and for allowing vertical adjustment of said supports.

6. A vacuum-type sheet feeding device as claimed in claim 5 wherein:

said adjustable lifter comprise vertically oriented rods with said supports positioned at the lower ends of said rods and with handles located at the upper ends of said rods; and

said rods are clamp-knob mounted to a stationary frame.

7. A vacuum-type sheet feeding device as claimed in claim 5 wherein is further included:

a magazine for holding said sheet stack, said magazine including a ledge for supporting one corner of said sheet stack; and

a separating means for disengaging the corner of the bottom sheet of said sheet stack from said ledge.

8. A vacuum-type sheet feeding device as claimed in claim 7 wherein said separating means comprises a reciprocating sucker cup which pneumatically grips the bottom sheet of said sheet stack and pulls said sheet off said ledge.

9. A vacuum-type sheet feeding device as claimed in claim 1 wherein a throat knife is positionable in front of said shuttle plate when said shuttle plate is under said sheet stack so that as said shuttle plate feeds said bottom sheet of said sheet stack, said elongated narrow groove is immediately adjacent to said throat knife and passes under said throat knife.

10. A vacuum-type sheet feeding device as claimed in claim 9 wherein said throat knife is elongated and an end tip thereof faces said groove, with the width of said throat knife being less than the width of said elongated narrow groove.

11. A vacuum-type sheet feeding device as claimed in claim 10 wherein said gate comprises two independently swinging half gates.

12. A vacuum-type sheet feeding device as claimed in claim 10 wherein a mounting means is included for said throat knife which allows selective movement of said throat knife to said active position and out of said active position.

13. A vacuum-type sheet feeding device as claimed in claim 12 wherein is further included:

a magazine for holding said sheet stack, said magazine including a ledge for supporting one corner of said sheet stack; and

a separating means for disengaging the corner of the bottom sheet of said sheet stack from said ledge.

14. A vacuum-type sheet feeding device as claimed in claim 10 wherein is further included:

a magazine for holding said sheet stack, said magazine including a ledge for supporting one corner of said sheet stack; and

a separating means for disengaging the corner of the bottom sheet of said sheet stack from said ledge.

15. A vacuum-type sheet feeding device as claimed in claim 10 wherein said throat knife is positioned such that said throat-knife end-tip protrudes into said elongated narrow groove when said shuttle plate feeds said bottom sheet, and said gate has an indentation formed at the top thereof to allow said gate to pass beneath said throat knife. 

1. A vacuum-type sheet feeding device for feeding the bottom sheet from a stack of flat sheets, said device comprising: a movable shuttle plate having a surface on which said stack rests, for gripping said bottom sheet and pulling said bottom sheet out of said sheet stack, said movable shuttle plate having motion in a direction substantially parallel to the plane of said flat sheets, said surface defining an elongated narrow groove therein which is elongated in a direction parallel to said direction of said shuttle-plate motion, and said narrow groove terminating at a back end thereof so that said back end is closed off and said groove extending to an edge of said shuttle plate at a front end thereof so that said front end is open; a gate mounted on said shuttle plate for closing off said groove near said front end, but for yielding to allow said bottom sheet to be sucked into said groove; and a pneumatic-suction means for creating a pneumatic suction in said groove to suck the bottom sheet into said groove; wherein said bottom sheet which is sucked into said groove is thereby adhered to said shuttle plate so that it moves with said shuttle plate.
 2. A vacuum-type sheet feeding device as claimed in claim 1 wherein said gate comprises two independently swinging half gates.
 3. A vacuum-type sheet feeding device as claimed in claim 1 wherein is further included; a magazine for holding said sheet stack said magazine including a ledge for supporting one corner of said sheet stack; and a separating means for disengaging the corner of the bottom sheet of said sheet stack from said ledge.
 4. A vacuum-type sheet feeding device as claimed in claim 3 wherein said separating means comprises a reciprocating sucker cup which pneumatically grips the bottom sheet of said sheet stack and pulls said sheet off said ledge.
 5. A vacuum-type sheet feeding device as claimed in claim 1 wherein is further included: a magazine for holding said sheet stack; and adjustable lifters for providing supports for each of the rear corners of said sheet stack and for allowing vertical adjustment of said supports.
 6. A vacuum-type sheet feeding device as claimed in claim 5 wherein: said adjustable lifter comprise vertically oriented rods with said supports positioned at the lower ends of said rods and with handles located at the upper ends of said rods; and said rods are clamp-knob mounted to a stationary frame.
 7. A vacuum-type sheet feeding device as claimed in claim 5 wherein is further included: a magazine for holding said sheet stack, said magazine including a ledge for supporting one corner of said sheet stack; and a separating means for disengaging the corner of the bottom sheet of said sheet stack from said ledge.
 8. A vacuum-type sheet feeding device as claimed in claim 7 wherein said separating means comprises a reciprocating sucker cup which pneumatically grips the bottom sheet of said sheet stack and pulls said sheet off said ledge.
 9. A vacuum-type sheet feeding device as claimed in claim 1 wherein a throat knife is positionable in front of said shuttle plate when said shuttle plate is under said sheet stack so that as said shuttle plate feeds said bottom sheet of said sheet stack, said elongated narrow groove is immediately adjacent to said throat knife and passes under said throat knife.
 10. A vacuum-type sheet feeding device as claimed in claim 9 wherein said throat knife is elongated and an end tip thereof faces said groove, with the width of said throat knife being less than the width of said elongated narrow groove.
 11. A vacuum-type sheet feeding device as claimed in claim 10 wherein said gate comprises two independently swinging half gates.
 12. A vacuum-type sheet feeding device as claimed in claim 10 wherein a mounting means is included for said throat knife which allows selective movement of said throat knife to said active position and out of said active position.
 13. A vacuum-type sheet feeding device as claimed in claim 12 wherein is further included: a magazine for holding said sheet stack, said magazine including a ledge for supporting one corner of said sheet stack; and a separating means for disengaging the corner of the bottom sheet of said sheet stack from said ledge.
 14. A vacuum-type sheet feeding device as claimed in claim 10 wherein is further included: a magazine for holding said sheet stack, said magazine including a ledge for supporting one corner of said sheet stack; and a separating means for disengaging the corner of the bottom sheet of said sheet stack from said ledge.
 15. A vacuum-type sheet feeding device as claimed in claim 10 wherein said throat knife is positioned such that said throat-knife end-tip protrudes into said elongated narrow groove when said shuttle plate feeds said bottom sheet, and said gate has an indentation formed at the top thereof to allow said gate to pass beneath said throat knife. 